This invention involves carbo-chlorination of aluminous material, and relates to previous patents assigned to Applied Aluminum Research Corporation which disclose novel processes for producing essentially pure, metallic aluminum from clay, bauxite, or other aluminous ores. In order to better understand how the invention described herein is to be utilized, it is desirable to briefly outline the main features of those several patents assigned to Applied Aluminum Research Corporation. The broad process divulged in these patents is also known as the "Toth Process", after its principal inventor, and in the descriptive material given below this terminology will be used.
In its most basic form, the Toth process consists of four prime steps:
I. carbo-chlorination of aluminous material to form aluminum trichloride; PA1 Ii reduction of the aluminum trichloride with manganese to form elemental aluminum and manganese dichloride; PA1 Iii. oxidation of manganese dichloride to give one or more forms of manganese oxide and chlorous gases; PA1 Iv. reduction of these manganese oxides to form manganese metal.
In the various processes previously patented, provision is made to recycle the manganese produced in Step IV for reutilization in Step II, and further to recycle chlorine liberated in Step III for reuse in Step I. Depending on the particular application, recycling may be external, or may be accomplished internally, as for example by the use of different reaction zones in a contactor. Recycling of these streams is necessary and desirable to minimize make-up costs for operation of the Toth process and to thus make the process economically competitive.
The four steps outlined above, in combination or separately, can be carried out in a variety of ways; U.S. Pat. Nos. 3,615,359, 3,615,360, 3,644,742, 3,713,809, and 3,713,811 give techniques for implementing the steps.
As can be seen from this brief description, carbochlorination of clay, bauxite, or other aluminous material is an integral and necessary part of the Toth process, and effective and economic means of carrying out Step I are necessary for the overall success of the Toth process. In the current invention, new and novel techniques are described for carrying out this carbo-chlorination of aluminous material.
In order to more fully comprehend how the current invention is related to past practice and technology, a brief description of earlier commercial processes for carbo-chlorination of aluminous materials will be given, to be followed by a description of the current invention.
Manufacture of aluminum trichloride (AlCl.sub.3) from aluminous materials is not new technology; it has been known and practiced for well over 100 years. At least two processes for such production have been operated commercially, the so-called Gulf and the Badische Anilin and Soda Fabrik (BASF) processes. In the Gulf process as developed and improved the following steps were employed: (1) coke and bauxite were ground, mixed, and calcined at approximately 770.degree.C in a rotary kiln to remove free and combined water and fully carbonize the coke, (2) the hot calcined mixture was stored and fed intermittently at 4-hour intervals to the chlorination reactors, (3) a chlorine-oxygen mixture was fed to the bottom of the chlorinator reaction vessels and feed rate was adjusted such that reaction of the chlorine was complete, and (4) AlCl.sub.3 vapor from the reactor system was condensed and collected. In the BASF process, chlorination was accomplished in the following fashion: (1) a mixture of carbon monoxide (CO) and chlorine (Cl.sub.2) was pretreated by heating to reactor temperature (approximately 900.degree.C) in a charcoal contactor; in addition to simply heating the mixture, partial conversion of these materials to phosgene was claimed to occur in this contactor, (2) the CO-Cl.sub.2 mixture was passed over a bed of either bauxite or alumina situated in a shaft furnace, and in which chlorination took place, and (3) AlCl.sub.3 vapor was recovered by subsequent condensation.
It is significant that in both of these cases of commercial production of AlCl.sub.3, high quality aluminous material (either bauxite or alumina) was used as the raw material. The following U.S. Pats. are exemplary of chlorination of clay, Nos. 1,238,604, 1,507,709, 1,858,252, and 2,238,421, however, none have been practiced commercially because of low conversion rates and poor yields. In view of highly limited domestic bauxite reserves, and concomitantly, the availability of large domestic clay deposits, it is apparent that effective techniques for chlorination of clay are highly desirable for future growth of the Toth process in the United States. Further, extensive clay deposits are to be found world-wide, and methods for clay chlorination would be applicable to these reserves.
In addition to the requirement of very high quality aluminous ores, the processes described above require high quality coke or charcoal as the reducing agent in the carbo-chlorination. Because of the much greater distribution and comparatively low costs of lower grade carbonaceous material (e.g. brown coal, lignite, etc.), methods of employing this material as a reducing agent would be highly desirable.
It is apparent from the foregoing discussion that effective carbo-chlorination of clay, or other aluminous material, by utilizing low grade coal as the carbon source, would be a valuable improvement to the Toth process. In addition, the AlCl.sub.3 so produced could find markets for many other purposes as well, including use in electrolytic methods for producing metallic aluminum from AlCl.sub.3 and uses as a catalyst in chemical and petroleum processing operations.